Method and apparatus for passing threadlike pieces through tubular products

ABSTRACT

A coil of a tube is formed. The coil is vibrated while a threadlike piece is passed in through the inlet end of the tube so that a given point of the tube reciprocates along a helical path. Provision is made to ensure that inlet end of the tube does not cause a portion of the threadlike piece upstream of and close to that inlet end to move diametrically while being fed into the tube. Provision is also made to form a coil of the treadlike piece, from which the threadlike piece is pulled out along the axis of the coil and fed to the inlet end of the tube by a conveying force resulting from the vibration of the coil of the tube. A feeder to supply the threadlike piece into the tube may be provided between the inlet end of the tube and a coil feeding device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for passing threadlikepieces through tubular products, and more particularly to a method andapparatus for passing threadlike pieces through tubular products byvibration.

The method and apparatus of this invention is used for making opticalfiber cables, electric cables, composite conduits and the likecomprising optical fibers, metal wires and other threadlike piecespassed through protective tubes or sheaths.

2. Description of the Prior Art

Threadlike pieces are often passed through long tubular products.Optical fiber cables recently coming into extensive use, for example,are often metal-covered to make up for the insufficient strength ofoptical fibers. In such instances, core wires or cords of optical fibersare passed through tubes not more than a few millimeters in diameter andover several hundred meters in length. Sometimes, a messenger wire ofsteel or other metal is passed before a core wire or cord is passed.

Typical conventional methods of making such products comprisingthreadlike pieces passed through metal and other tubes are disclosed inEPC Patent No. 91717 and Japanese Provisional Patent Publication No.44010 of 1987. In these methods, carrier members or tubes (hereinaftergenerically called tubes) through which threadlike pieces are passed arevibrated. A threadlike piece is passed through a tube by means of thecarrying force imparted thereto on the "vibrating conveyor". When a tubeis as long as, for example, over tens of meters, the tube is coiled forease of handling, and a threadlike piece is passed through the coiledtube.

A threadlike piece passed through a long tube according to suchconventional methods often stops part way through. The threadlike pieceonce stopped remains at a standstill even if the vibration of the tubecontinues. On the occurrence of such a blockage, the entire length ofthe inserted threadlike piece or a considerably large portion thereofhas had to be pulled out of the tube for starting the job all overagain. As such, conventional methods of passing threadlike piecesthrough long tubes have been inefficient and time-consuming. Thefollowing is the cause for the stopping of a threadlike piece part ofthe way through a tube the inventors have found.

In the conventional methods, the inlet end of a tube vibrates integrallywith a coil. The vibrating inlet end coming in contact with a threadlikepiece exerts a force thereon that works in the direction of the diameterof the tube. Therefore, a portion of the threadlike piece upstream ofand close to the inlet end of the tube moves vigorously in thatdirection. As a consequence, a centrifugal force flicks the portion ofthe threadlike piece near the inlet end out of the tube, therebyobstructing the further advance of the threadlike piece into the tube.Also, the rapid diametrical motion of the inlet end causes the sameportion to remain ahead of the inlet end, thereby discharging thethreadlike piece in the tube. Furthermore, the vibration repeatedlybends and damages the threadlike piece near the inlet end of the tube.Microcracks are a typical damage to optical fibers, in particular. Thevibration-induced contact with the inlet end of the tube can produce anabrasion on the surface of the threadlike piece.

Usually, a threadlike piece paid off from a spool or bobbin is fed to atube into which the piece is to be passed. If the pay-off (or the feed)of the threadlike piece from the spool etc. lags, for some reason,behind the travel forward by vibration, the threadlike piece is pulledbackward, no longer advancing into the tube.

A threadlike piece winds forwards with undulating motion through a tube.The advance of the forward end of the threadlike piece lags behind thatof the following portion or stops when the forward end trips againstirregularities on the inner surface of the tube or foreign matterstherein, or when it is subjected to a backward force from near the topsurface of the inner wall. Pushed by the following portion, the forwardend of the threadlike piece on such occasions suddenly makes heavyundulations. Consequently, peaks of such undulations in the forward endof the threadlike piece strike hard against the inner wall of the tube,offering sufficient resistance to suddenly prevent the further passingof the threadlike piece therethrough.

The part way stalling of a threadlike piece in a tube is due to any oneof or a combination of the three causes just described.

SUMMARY OF THE INVENTION

The object of this invention is to provide a method and apparatus forefficiently passing a threadlike piece through a tube without damagingthe threadlike piece.

A method of passing a threadlike piece through a tube according to thisinvention comprises forming a coil of tube and vibrating the coil oftube while feeding a threadlike piece from an inlet end of the tube sothat a given point of the tube reciprocates along a helical path. Thethreadlike piece is fed in such a manner that the inlet end of the tubedoes not impart a diametrical motion to a portion of the threadlikepiece upstream of and close to the inlet end.

The threadlike piece may instead be pulled out and fed from a coilthereof along the axis of the coil by use of a carrying force resultingfrom vibration that works on the threadlike piece in the tube. Also, thefeed rate of the threadlike piece may be adjusted at a point upstream ofthe inlet end of the tube so that the feed rate of the threadlike piecedetermines the passing rate thereof.

A coil of tube is made by winding a tube around a cylindrical core suchas a bobbin or a spool. A tube may instead be formed into a core-lesscoil. To facilitate passing and avoid the imposition of excessivebending stress of the threadlike piece, a coil of tube should preferablyhave a diameter of not smaller than 150 mm.

A threadlike piece is fed from a spool on which the thread is wound, ora bobbin at a standstill, or a container holding a coil thereof. Thespool may be rotated to permit a positive feed of a threadlike piecetherefrom at a speed equivalent to that of conveyance owing tovibration. The feed rate of the threadlike piece, which determines thespeed of the threadlike piece passed by vibration, is either faster orslower than the passing rate thereof. A feeder provided between thespool or the like and the inlet end of a tube controls the feed rate ofa threadlike piece so that the feed rate determines the passing ratethereof. When a driven spool is used, the feed rate of a threadlikepiece is adjusted by controlling the rotating speed of the spool. Thefeed rate may also be controlled by means of the friction between athreadlike piece and a guide to provide a support thereto that isprovided upstream of the inlet end of a tube. For instance, the feedrate is decreased by increasing the friction therebetween. When therotating speed of a spool is controlled and the friction of a guide isused, the feed rate of a threadlike piece cannot be made faster than therate of conveyance by vibration. A threadlike piece may be sent to theinlet end of a tube by means of a feeder either only during the earlystage of passing or continuously throughout the entire period ofpassing. In the latter case, the feeder pushes a threadlike piece into atube through the inlet end thereof, passing the threadlike piecetherethrough at a speed equal to the feed rate of the feeder. Using afeeder, the feed rate of a threadlike piece may also be kept below thespeed of conveyance by vibration.

A coil of tube, which is either core-less or wound around a cylindricalcore, can be vibrated by oscillating a member that holds or supports thecoil by such known devices as a vibrating motor or an electromagneticvibrator. The angle of vibration (i.e., the lead angle of the helix),the frequency of vibration and the total amplitude of vibration in termsof vertical component are preferably between 5 degrees and 30 degrees,between 10 Hz and 30 Hz, and between 0.2 mm and 2.0 mm, respectively. Anultrasonic oscillator may be used, too.

To ensure that the inlet end of a tube does not diametrically move aportion of a threadlike piece upstream of and close to the inlet end,the inlet end of the tube is immovably fastened to the floor or suitablestructure or device therearound. Also, the inlet end of a tube may beheld in such a manner as to allow the longitudinal motion of the tubewhile restraining the diametrical motion thereof. Otherwise, a guidethat extends substantially horizontally and opening upward may beconnected to the inlet end of a tube so that the guide vibratesintegrally with a coil of the tube. A threadlike piece passed into theguide from about through the opening at the top is then led to the inletend of the tube.

An apparatus for passing a threadlike piece through a tube according tothis invention comprises a cylindrical member around which a tubethrough which a threadlike piece is to be passed is wound to form a coilthereof, a device to hold the inlet end of the tube so that the inletend thereof does not diametrically move a portion of the threadlikepiece upstream of and close to the inlet end of the tube, a device tovibrate the cylindrical member so that a given point of the tubereciprocates along a helical path, and a device to feed the threadlikepiece into the coil of tube being vibrated from one end thereof.

In the apparatus just described, the device to hold the inlet end of atube may be eliminated. Then, the threadlike piece feeding device holdsa coil of a threadlike piece and feeds a threadlike piece, which ispulled out along the axis of the coil thereof by the vibration-inducedcarrying force acting on the threadlike piece in the tube, to the inletend of a tube. The threadlike piece feeding device may be of such designas to control the feed rate of a threadlike piece at a point upstream ofthe inlet end of a tube so that the feed rate of the threadlike piecedetermines the passing rate thereof. Furthermore, the inlet end holdingdevice and any of the threadlike piece holding devices just describedmay be combined into a single integral unit.

When a coil of tube is vibrated by the method and apparatus of thisinvention just described so that a given point of the tube reciprocatesalong a helical path, the inner wall of the tube exerts on thethreadlike piece in the coiled tube a force that works in a diagonallyforward and upward direction. Therefore, this force causes thethreadlike piece in the tube to jump or slide along the inner wall ofthe tube in a diagonally forward and upward direction. Thus, the innerwall of the tube intermittently exerts a carrying force, which works inthe direction of the circumference of the coil, on the threadlike piecein the tube to cause the threadlike piece to advance therethrough.

When the inlet end of the tube is firmly held, no centrifugal forceworks on the threadlike piece near the inlet end. Therefore, thethreadlike piece does not jump out of the tube. Prevented from making asudden diametrical motion, in addition, the threadlike piece near theinlet end is neither caused to remain ahead of the inlet end nor to bedamaged.

When a threadlike piece to be fed to the tube is pulled out from a coilthereof along the axis of the coil, there is no need to rotate a spooland the coil wound therearound. Only a small amount of force is requiredfor pulling out the threadlike piece from the coil. Therefore, thecarrying force produced by vibration is enough for feeding thethreadlike piece to the inlet end of the tube. The force to pull out thethreadlike piece from the coil is not only small as mentioned above butalso substantially constant. Such a force assures a stable feed of thethreadlike piece to the inlet end of the tube, reducing the risk of thethreadlike piece being passed stopping part way through the tube.

When the feed rate of a threadlike piece determining the passing speedof the threadlike piece is faster than the speed of the threadlike piecepassed forward by vibration, the threadlike piece is forced into thetube through the inlet end thereof. Vibration not only generates acarrying force, but also facilitates the insertion of the threadlikepiece by reducing the friction between the threadlike piece and theinner surface of the tube. The force needed for the forcible insertionmust be great enough to overcome the frictional resistance the innersurface of the tube offers to the threadlike piece travellingtherethrough and, at the same time, small enough not to break thethreadlike piece. A proper amount of pushing force permits thethreadlike piece to be passed forward at a higher speed than the speedattained with the conveyance by vibration alone. Pushing with such aforce is also an effective way to overpower the frictional resistanceoffered by the inner surface of the tube. Conceivably, on the otherhand, frictional resistance increases with an increase in the length ofa threadlike piece passing through a tube. Therefore, effectiveness offorcing in the threadlike piece disappears beyond a certain point. Assuch, the choice of a proper pushing force and speed requires carefulconsiderations of such points. Generally, the risk of stopping part waythrough is smaller with the forced-in threadlike piece. Because of theaforementioned limit in applicable length, however, this method issuited only for tubes not longer than several hundred meters. When, onthe other hand, the feed rate of a threadlike piece is slower than thespeed of the threadlike piece, the threadlike piece in the tube ispulled backward. This backward pulling reduces the undulation of thethreadlike piece in the tube. The lessened undulation, in turn,decreases or eliminates the friction between the inner surface of thetube and the leading end of the threadlike piece at the peak ofundulation. This substantially completely eliminates the risk of partway stopping.

The method and apparatus of this invention assures efficient passing ofa threadlike piece through a tube without causing degeneration anddamage, even if the tube diameter is small (e.g., 2 mm or under inoutside diameter) and the tube length is large (e.g., 1 km or over inoverall length).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation showing a first preferred embodiment of anoptical fiber passing apparatus according to this invention;

FIG. 2 is a plan view of a vibrating table of the same apparatus;

FIG. 3 is a vertical cross-sectional view showing how the inlet end of atube is fastened;

FIGS. 4 and 5 illustrate how an optical fiber is carried forward at theinlet end of a tube. FIG. 4 shows a case according to this invention,whereas FIG. 5 a case with a conventional method;

FIG. 6 is a side elevation showing a second preferred embodiment of anoptical fiber passing apparatus according to this invention;

FIG. 7 is side elevation showing a third preferred embodiment of anoptical fiber passing apparatus according to this invention;

FIG. 8 is a perspective view illustrating a method of forming a coil ofoptical fiber;

FIGS. 9(a) and 9(b) illustrate how an optical fiber is carried forwardat the inlet end of a tube;

FIG. 10 is a side elevation showing a fourth perferred embodiment of anoptical fiber passing apparatus according this invention;

FIG. 11 is a side elevation showing a fifth preferred embodiment of aoptical fiber passing apparatus according to this invention;

FIG. 12 is a plan view of a vibrating table of the apparatus shown inFIG. 11;

FIG. 13 is a detail view of a roll feeder and a tube holder on theapparatus shown in FIG. 11;

FIG. 14 illustrates how an optical fiber is carried forward at the inletend of a tube on the apparatus shown in FIG. 11;

FIG. 15 shows the condition of an optical fiber in the tube, withdifferent surplus lengths;

FIG. 16 is a side elevation showing a sixth preferred embodiment of anoptical fiber passing apparatus according to this invention;

FIG. 17 is a side elevation showing a seventh preferred embodiment of anoptical fiber passing apparatus according to this invention;

FIG. 18 is a perspective view of an optical fiber guide attached to abobbin on the apparatus shown in FIG. 17;

FIG. 19 illustrates how an optical fiber is carried forward at the inletend of a tube on the apparatus shown in FIG. 11;

FIG. 20 is a side elevation showing an eighth preferred embodiment of anoptical fiber passing apparatus according to this invention;

FIG. 21 is a side elevation showing a ninth preferred embodiment of anoptical fiber passing apparatus according to this invention; and

FIG. 22 is a side elevation showing a tenth preferred embodiment of anoptical fiber passing apparatus according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In all preferred embodiments of this invention to be describedhereunder, an optical fiber is passed through a steel tube.

PREFERRED EMBODIMENT I

A preferred embodiment of an apparatus to implement a passing method ofthis invention will be described first. FIG. 1 is an overall view of apassing apparatus according to this invention, and FIG. 2 is a plan viewof a vibrating table on the same apparatus.

A base 11 is firmly fastened to the floor 10 so as not to vibrate. Coilsprings 18 to support a vibrating table are mounted at the four cornersof the top surface of the base 11.

A flat square vibrating table 14 is placed on the base 11, with thesupport springs 18 interposed therebetween. A support frame 15 extendsdownward from the bottom surface of the vibrating table 14.

The support frame 15 under the vibrating table 14 carries a pair ofvibrating motors 21, 22. The vibrating motor 22 is placed diametricallyopposite the motor 21 relative to the central axis C of the table 14.The rotating shafts of the vibrating motors 21, 22 are respectivelyparallel to a vertical plane containing the central axis C andoppositely tilted with respect to the surface of the vibrating tableeach at an angle of 75 degrees. Unbalanced weights 24 are fastened toboth ends of the rotating shafts of the vibrating motors 21, 22. Thecentrifugal force resulting from the rotation of the unbalanced weights24 exerts a vibrating force on the vibrating table 14 that works aslantto the surface thereof. The paired vibrating motors 21, 22 are driven insuch a manner that the vibrations they make have an equal frequency andamplitude, and the vibrating forces they exert are displaced 180 degreesaway from each other. When the vibrations caused by the paired motors21, 22 are combined, the vibrating table 14 vibrates in such a manner asto move along a helical path whose central axis coincides with thecentral axis C of the vibrating table 14. But the vibration of thevibrating table 14 is not transmitted to the base 11 because of thesupport springs 18 interposed therebetween.

Such vibrating means as those employing cranks, cams or electromagnetsmay be used in place of the vibrating motors 21, 22. Also, the vibratingmotors 21, 22 may be attached to the vibrating table 14 in other waysthan that shown in the figures.

A bobbin 27 is fastened on the vibrating table 14 in such a manner thatthe axis thereof coincides with the central axis C of the vibratingtable 14. A tube 1 through which an optical fiber 7 is to be passed iscoiled around the bobbin 27. The optical fiber 7 is fed into the tube 1from the upper end of a coil 6 of the tube. To ensure that no excessivebending stress develops in the optical fiber, the coil 6 of the tubeshould preferably have a diameter of not smaller than 150 mm. Theoptical fiber 7 used in this embodiment consists of an element opticalfiber precoated with resin. The tube 1 is a steel tube. The outerperiphery of the bottom flange 29 of the bobbin 27 is fastened to thevibrating table 14 with fastening jigs 31 so that the vibration of thevibrating motors 21, 22 is surely received. The bobbin 27 has a groove(not shown) cut around the circumference thereof, with successive ridgesand recesses pointing toward the axis thereof. The groove is designed sothat the tube 1 comes in close contact therewith.

A feed spool 34, which constitutes an optical fiber feeder 33, is placedbeside the bobbin 27. The feed spool 34 is rotatably supported on abearing stand 35. The feed spool 34 pays off the optical fiber 7 woundtherearound to the flared inlet end 3 of the tube.

A drive motor 38 is provided next to the feed spool 34. The feed spool34 and drive motor 38 are interlocked through a belt transmission 40.Rotated by the drive motor 38, the feed spool 34 pays off the opticalfiber 7 to the tube 1 wound around the bobbin 27.

A cylindrical support guide 43 is provided near the point where the feedspool 34 pays off an optical fiber. The support guide 43 supports theoptical fiber 7 paid off from the feed spool 34.

An optical fiber feed condition sensor 47 is installed downstream of thesupport guide 43. The optical fiber feed condition sensor 47 comprises asupport column 48 and an optical fiber level sensor 49 attached thereto.The optical fiber level sensor 49 comprises an image sensor and anoppositely disposed light source. Installed in the pass line of theoptical fiber 7, the optical fiber level sensor 49 senses the saggingcondition thereof. A CCD line sensor is used as the image sensor.

To the optical fiber feed condition sensor 47 is connected a rotationspeed controller 52 that controls the voltage of a power supply 39 tosaid drive motor 38 on the basis of signals from the optical fiber feedcondition sensor 47. The rotation speed of the drive motor 38 or, inother words, the pay-off speed of the optical fiber 7 is controlledaccording to the level at which the optical fiber 7 interferes with thetravel of the light from the light source in the optical fiber levelsensor 49.

The speed with which the optical fiber 7 is passed through the tube 1 isnot always constant but may vary when resonance occurs or depending onthe surface condition of the inner wall of the tube 1 and the opticalfiber 7. A change in the running speed of the optical fiber 7 in thetube 1 affects the feeding condition of the optical fiber 7 on theoutside. If the feed speed fails to follow the passing speed, theoptical fiber 7 may either sag excessively or overstretch and break,hindering smooth feeding of the optical fiber 7. But the feed speed ofthe optical fiber 7 can always be kept within the desired range byvarying or stopping the rotation of the feed spool 34 depending on thetravelling condition of the optical fiber 7 in the tube 1. Then, theoptical fiber 7 is kept in the optimum condition (with a slight saggingas shown in FIG. 1), without oversagging or over-stretching.Consequently, the optical fiber 7 is passed through the tube 1 without ahitch, with no load imposed thereon or no resistance offered to thepassage thereof. Incidentally, an optical fiber 0.4 mm in diameter doesnot go into a steel tube having an inside diameter of 0.5 mm if a forceof 20 gf or greater works thereon in a direction opposite that offeeding.

A cylindrical support guide 54 and an electromagnetic feeder 55 areprovided on the exit side of the optical fiber feed condition sensor 47.The electromagnetic feeder 55 sends an optical fiber 7 from the supportguide 54 to the flared end 3 of the tube.

The inlet and outlet of the support guides 43 and 54 should preferablyhave a smooth curved surface. The support guides 43 and 54 must be madeof such materials as glass and plastic whose coefficient of friction islow enough to assure a smooth travel of the optical fiber 7. Porvisionmay be made to supply a solid lubricant such as a powder of carbon,talc, molybdenum disulfide, etc. to the surface of the optical fiber 7travelling through the support guides 43, 54.

A metal tube holder 57 is provided on the exit side of theelectromagnetic feeder 55. The inside of the metal tube holder 57 isfunnel-shaped as shown in FIG. 3.

Now a method of passing an optical fiber 7 through a tube 1 using theabove-described apparatus will be described.

A coil 6 is formed in advance by winding a tube 1 around a bobbin 27.The tube 1 wound around the bobbin 27 need not always be in a singlering, but can be in multiple rings. In a coil of multiple rings, thefirst ring fits closely in a groove cut in the surface of the bobbin 27.The second and subsequent rings are arranged to fit in the recessesformed between the turns of the tube 1 of the preceding ring. Then, thebobbin 27 carrying the wound tube 1 is fastened on the vibrating table14 in such a manner that the axis of the coil coincides with the centralaxis C of the vibrating table 14.

A suitable length of the tube is cut off from an unwound ring of thecoil 6 following the lead-in section 2 thereof. The cut off length ofthe tube is curved in a horizontal plane. Then, the inlet end 4 of thetube passed through a guide hole 58 in the metal tube holder 57 isflared into a funnel-shape, and fastened to the metal tube holder 57with a metal fastener 59. The remotest end 5 of the lead-in section 2 isfastened to the flange 29 of the bobbin 27 with a metal fastener 61.

An optical fiber 7 consisting of a precoated element fiber, is woundaround the feed spool 34. The leading end 8 of the optical fiber 7pulled out of the feed spool 34 is inserted through the metal tubeholder 57 into the inlet end 4 of the tube, after passing through thesupport guide 43, optical fiber feed condition sensor 47, support guide54 and feeder 55.

The drive motors 21, 22, the feeder 55 and the drive motor 38 of thefeed spool 34 are started in that order.

With the drive motors 21, 22 attached to the vibrating table 14 in theplace and position described previously, the vibrating table 14 is thensubjected to a torque working around the central axis C thereof and aforce working therealong. Consequently, a given point on the vibratingtable moves along a helix H shown in FIG. 1. The vibration V thusproduced is transmitted from the vibrating table 14 through thefastening jigs 31, the bobbin 27 and the coil 6 of tube to the lead-insection 2 thereof.

Referring now to FIGS. 3 and 4 (in FIG. 4, the curved lead-in section 2of the tube is shown as a straight tube for convenience's sake), it willbe described how the optical fiber 7 enters the tube 1 when the passingoperation is started. The lead-in section 2 has a midway transitionpoint T where the direction of vibration coincides with the center ofthe curvature of the inlet 2. In the section (hatched in FIG. 3) betweenthe flared end 3 and the transition point T, vibration transmitted fromthe inner wall of the tube to the optical fiber 7 produces no conveyingforce. In this section, the pushing force of the feeder 55 sends theleading end of the optical fiber 7 forward. Also in this section,vibration keeps the optical fiber 7 from sliding along the inner wall ofthe tube, reduces the friction between the optical fiber 7 and the innerwall of the tube, and facilitates the forward motion of the leading endof the optical fiber 7 pushed by the feeder 55.

In the section between the transition point T and the remotest end 5 ofthe lead-in section 2 end, the conveying component of vibrationincreases progressively. The optical fiber 7 behind this section, orbetween the flared end 3 and the transition point T, is inside the tubeand under the influence of the driving force of the feeder 55.Therefore, no force to prevent advance (owing to both the effect ofcentrifugal force and the static inertia of the optical fiber behind)works on the leading end of the optical fiber 7 in this section. Assuch, the leading end of the optical fiber 7 advances if the vibratingtube exerts any conveying force at all on the optical fiber 7 (or if theangle between the directions of vibration and passing is acute). Theconveying force resulting from vibration carries the optical fiber 7forward after the leading end thereof has passed the transition point T.When the leading end reaches the remotest end 5 of the inlet 2, theremotest end 5 lies at the uppermost end of the coil 6, where theoptical fiber 7 is passed into the tube 1 substantially along a linetangent to the coil 6. Once the optical fiber 7 has thus been properlypassed into the tube 1, the rotation of the feeder 55 is stopped.Afterward, the feeder 55 serves as a holding guide.

With the technology disclosed in EPC Patent No. 91717, incidentally, theleading end of an optical fiber is inserted a given distance L beforepassing is started, as shown in FIG. 5. Accordingly, conveying forceproduced by vibration must be exerted on the optical fiber 7 at theflared end 3 to make the conveying force great enough to overcome aforce owing to the effect of centrifugal force and a force owing to thestatic inertia of the optical fiber 7 behind the inlet end 3. Theconveying force resulting from vibration becomes equal to the combinedforce to prevent the advance of the optical fiber at point P. Saiddistance L is greater than the distance between point P and the flaredend 3 of the tube. The optical fiber does not advance while the leadingend thereof stays upstream of point P. It is not until the leading endhas passed point P that the optical fiber begins to move forward.

As is obvious from FIGS. 4 and 5, the conventional method inserts aconsiderable length of optical fiber into the tube before startingpassing. By contrast, the preferred embodiment of this invention beingdescribed does not require such preliminary insertion.

Driven by a component of the force exerted by the inner wall of the tube1 which works in the circumferential direction of the coil, the opticalfiber 7 in the coil 6 of the tube moves further into the tube. Becausethe axis of the coil coincides with the central axis C of the vibratingtable 14, the optical fiber 7 in the tube moves in a circle about thecentral axis C (in the clockwise direction P in the embodiment shown inFIG. 2).

Reference is now made back to FIG. 1.

When the helical vibration is transmitted through the vibrating table 14to the coil 6 of the tube, the optical fiber 7 fed from the flared end 3of the tube above the coil 6 continuously moves forward through thetube 1. That is, the vibration of the coil 6 moves the optical fiber 7paid off from the feed spool 34 forward through the support guide 43,optical fiber feed condition sensor 47, support guide 54, feeder 55,flared end 3 of the tube, inlet 2, coil-formed tube 1, and outlet end ofthe tube. Thus, the optical fiber 7 is passed through the entire lengthof the coil 6 of the tube in a given time. Because the inlet end 4 thetube is fastened, the flared end 3 causes no damage to the optical fiber7.

Any variation in the passing speed of the optical fiber 7 affects thefeed condition thereof at the point where the optical fiber level sensor49 is installed, with the resulting change in the feed condition beinginstantly detected by the optical fiber level sensor 49. If the opticalfiber level sensor 49 senses that the optical fiber 7 is overstretched,a corresponding signal will be sent to the drive motor 38 to increasethe rotation speed of the feed spool 34, thereby increasing the feedspeed of the optical fiber 7. If an excessive sagging of the opticalfiber 7 is sensed, the drive motor 38 will be controlled to slow downthe feed speed of the optical fiber 7. In this way, any abnormalcondition in the forward travel of the optical fiber is instantlysensed, corrected and returned to the normal condition.

PREFERRED EMBODIMENT II

FIG. 6 shows another embodiment of this invention. In all of thefollowing embodiments, the devices and members similar to those shown inFIGS. 1 to 3 will be designated by the same reference numerals, with adetailed description thereof omitted.

In this second preferred embodiment, the optical fiber 7 paid off fromthe coil 9 thereof drops into the lead-in section 2 of the tube underits own weight.

A frame 64 is fastened to the floor 10 diagonally above a vibratingtable 14. A bobbin 66 around which an optical fiber 7 is wound is placedon the frame 64.

An optical fiber guide 68 is provided next to the frame 64. The opticalfiber guide 68 has a guide tube 70 supported by a bracket 69. The guidetube 70 consists of a vertical portion 71 and a curved portion 72 curveddiagonally downward. The upstream end of the curved portion 72 of theguide tube 70 opens diagonally downward. The surface of the frame 64 onwhich the bobbin is placed is tilted so that the axis of the coil of theoptical fiber faces the opening of the curved portion 72 of the guidetube 70.

A metal tube holder 74 is provided next to the optical fiber guide 68 onthe exit side thereof. The metal tube holder 74 has a through hole 75.Because the end 3 of the tube passed through the through hole 75 isflared, the inlet end 4 of the tube is firmly held in the through hole75. As such, the inlet end 4 of the tube held by the metal tube holder74 does not move, either diametrically or longitudinally.

The tube 1 is wound around the bobbin 27 to form a coil 6 of the tube,with the last ring thereof fastened with an adhesive tape 30. Thelead-in section 2 of a given length is unwound from the coil, curvedupward and extended. The inlet end 4 is fastened to the metal tubeholder 74. A coil 9 of the optical fiber 7 is as wound at the fibermanufacturer. The forward end of the optical fiber 7 paid off from thebobbin 66 is passed into the inlet end 4 through the guide tube 70.Then, drive motors 21, 22 are started. A reversed torsion, which will bedescribed later, is not given to the optical fiber 7 wound into the coil9.

The optical fiber 7 falls under gravity through the vertical portion 71of the guide tube 70 and the lead-in section 2 of the tube 1. As such,this embodiment reduces the load to be borne when the optical fiber 7 isunwound from the coil 9 and the length of the optical fiber 7 to bepassed in initially.

PREFERRED EMBODIMENT III

FIG. 7 shows a third embodiment of this invention. In this embodiment,the inlet end of a tube is held in such a manner as not to permit onlydiametrical motion. Longitudinal motion is permitted. Also, a feeder isprovided to push an optical fiber into the tube, which permits passingthe optical fiber through the tube at a speed faster than the speed ofconveyance by vibration. But this embodiment is not applicable to longertubes whose length exeeds several hundred meters because of the limit inthe passable length of the optical fiber mentioned previously.

As shown in the figure, an optical fiber container 77 is provided besidethe bobbin 27. The optical fiber container 77 consists of a cylindricalcontainer proper 78 having an open top. The container 77 contains anoptical fiber 7 that is fed into the container proper 78 that is mountedand rotated on a turn table (not shown), as will be described later.

An optical fiber guide 81 is disposed next to the optical fibercontainer 77. The optical fiber guide 81 has a guide tube 83 supportedon a stand 82. The downward-curved inlet end of the guide tube 83 openstoward the optical fiber container 77 substantially on the central axisthereof.

A belt feeder 86 is disposed on the exit side of the optical fiber guide81. The belt feeder 86 comprises a pair of endless belts 88, one lyingon top of the other, on a table 87. Driven by motor-powered pulleys 89,the belts 88 send the optical fiber 7 held therebetween from the opticalfiber guide 81 held therebetween to the inlet end 4 of the tube.

A cylindrical metal tube holder 92 is placed on the exit side of thebelt feeder 86. The inlet end 4 of the tube is passed through the metaltube holder 92 whose inside diameter is somewhat larger than the outsidediameter of the tube 1. Though allowed to slide longitudinally, theinlet end 4 of the tube is not permitted to move diametrically, i.e., upand down and sidewise.

The following is a method of passing an optical fiber 7 through a tube 1using the above-described apparatus.

While a coil 6 of the tube is formed, a coil 9 of the optical fiber 7 isformed inside the optical fiber container 77 by laying up piles thereof.A bobbin 27 carrying a coil of the tube 1 is fastened to a vibratingtable 14 with through bolts 32. The optical fiber 7 is pulled up to alevel above the optical fiber container 77, proceeding downward from theuppermost loop of the coil 9. On this occasion, each loop of the opticalfiber 7 is twisted 360 degrees maximum. To regain the originalcondition, the twisted optical fiber warps inside the tube 1, offering aresistance to coveyance. Therefore, a reversed twist should preferablybe given to the optical fiber 7 when it is fed into the container 77 sothat the twist the optical fiber 7 receives on being unwound is offset.The optical fiber thus kept in a container does not curl like the onewound around a spool or the like.

FIG. 8 shows a method of giving a reversed twist to an optical fiber 7.The optical fiber 7 is fed through a guide tube 96, caterpillar feeder95 and a rotating guide tube 97 into the container proper 78 of theoptical fiber container 77. The rotating guide tube 97 is eccentric tothe container proper 78 by a distance δ, and is rotated by a motor (notshown) through a gear transmission 98. The container proper 78 and therotating guide tube 97 are rotated in the same direction, about thecentral axes X and Y thereof. Fed from the rotating guide tube 97, theoptical fiber 7 is circumferentially piled up from the bottom of thecontainer proper 78 to form a coil, becoming progressively eccentric bya width of 2δ. If the rotating speed of the container proper 78 is V_(P)and that of the rotating guide tube 97 is V_(G), the angle of a reversedtwist θ=360° (1-V_(P) /V_(G)). If the rotating speed V_(P) of thecontainer proper 78 is made sufficiently smaller than the rotating speedV_(G) of the rotating guide tube 97, the angle of the reversed twist θbecomes substantially equal to 360 degrees. Therefore, the optical fiber7 forms no kink when unwound from the coil 9.

Then, a given length of the optical fiber 7 taken out of the container77 is passed through the optical fiber guide 81, the belt feeder 86 andthe flared end 3 of the tube until the leading end 8 of the opticalfiber 7 enters the tube 1.

When preparations for passing are completed, the vibrating motors 21, 22and belt feeder 86 are started.

Referring now to FIGS. 9(a) and 9(b), the advance of the optical fiber 7into the tube 1 will be described. Because the metal tube holder 92firmly holds the inlet end 4, the lead-in section 2 does not move up anddown and sidewise, though vibrating longitudinally. Therefore, nodriving force f owing to vibration works on the optical fiber 7 at thelead-in sectin 2 of the tube 1. The advance of the optical fiber 7 inthis region is solely due to the pushing force F exerted by the beltfeeder 86.

In the coil 6 of the tube 1 lying beyond the remotest end 5 of thelead-in section 2, the tube 1 vibrates helically, and the inner wallthereof pushes the optical fiber 7 up and diagonally forward. Therefore,the optical fiber 7 jumps, or slides along the inner wall of the tube,diagonally forward. Thus, a circumferential component of the forceexerted by the inner wall of the tube 1 and a pushing force exerted bythe belt feeder 86, in combination, cause the optical fiber 7 to travelforward in the tube. That is, the two forces produced by vibration andexerted by the feeder move the optical fiber 7 forward through the tube.

The optical fiber 7 pushed by the belt feeder 86 into the flared end 3of the tube will encounter the following resistances:

(a) Resistance with the friction with the tube wall offers to forwardtravel;

(b) Resistance with the coiled tube offers to forward travel;

(c) Resistance with the kinked optical fiber offers to forward travel;and

(d) Backward force from near the top of the inner wall of the tube.

Resistances (b) and (c) work to increase the frictional resistance (a).

Because resistance (b) is greater in the coiled tube 1 than in astraight tube, transmission of the pushing force from the flared end 3throughout the entire length of the optical fiber is not as easy.However, the helical vibration of the coil 6 produces an equal (uniform)vibration at all points of the tube 1. The vibration is a simpleharmonic motion slanting in the longitudinal direction of the tube,having a horizontal component tangential to the coil 6 of the tube andexerting a driving force f on the optical fiber 7. The driving force fworks tangentially to the coil 6 of the tube at all points thereof.Therefore, the driving force f always works on the optical fiber 7 inthe tube 1 in the longitudinal direction thereof or in the direction oftravel. Working along the curve of the tube, the driving force f reducesthe friction owing to vibration and keeps the optical fiber 7 fromgetting pressed against the tube wall. In other words, the driving forcef works to keep the optical fiber 7 from getting out of the right path.The optical fiber 7 pushed by force F into the curved tube from theflared end 3 moves forward as if it was traveling through a straighttube under the influence of the driving force f. The vibration of thetube 1, of course, reduces the friction between the optical fiber andthe tube wall. The method of this invention, therefore, overcomes theresistance (a) from the friction with the tube wall by vibration and theresistance (b) owing to the curved tube 1 by a combination of vibrationand the driving force f. Keeping the optical fiber 7 in the tube fromsagging, the driving force f assures easier transmission of the pushingforce F throughout the entire length of the optical fiber. Theresistance (c) owing to the kink of the optical fiber can also beovercome by feeding a pre-twisted optical fiber 7 from a coil 9 held inthe optical fiber container 77. The optical fiber 7 kept in thiscondition has no tendency to kink. The frictional resistance (a) fromthe tube wall can be reduced by applying a lubricant on the surface ofthe optical fiber, too. The resistance (b) owing to the curved tube canalso be reduced by increasing the coil diameter.

Allowed to move in the longitudinal direction of the tube 1, the inletend 4 thereof is less subjected than otherwise to the repeated bendingforce exerted by the vibrating tube 1, thus remaining undamaged.

PREFERRED EMBODIMENT IV

FIG. 10 shows still another embodiment of this invention. In thisembodiment, the inlet end of the tube is firmly held. A conveying forceresulting from vibration pulls out an optical fiber from a coil thereof.

An optical fiber container 77 and an optical fiber guide 81 are placedbeside a bobbin 27.

A tube holder 101 is placed next to the optical fiber guide 81 on theexit side thereof. The tube holder 101 has a casing 103 supported by astand 102, with guide rolls 104 rotatably set in the casing 103. Theguide rolls 104 are paired in such as manner as to hold a tube 1therebetween. The pairs of guide rolls are alternately set in thevertical and horizontal positions. As such, the inlet end 4 of the tubeheld by the tube holder 101 is allowed to move longitudinally, but notdiametrically.

By winding a tube 1 around the bobbin 27, a coil 6 of the tube is formedin advance. A ring of the tube 1 making up the lead-in section 2 thereofis then unwound from the coil 6 and cut to a suitable length. Thelead-in section 2 of the tube 1 is then pulled from the coil 6 to thetube holder 101. After the inlet end 4 has been passed through the tubeholder 101, the foremost end 3 of the tube is flared into a funnel-likeshape. The remotest end 5 of the lead-in section 2 is immovably fastenedto the flange 29 of the bobbin 27 with a metal fastener 61. An opticalfiber 7 is placed in the optical fiber container 77.

A given length of the optical fiber 7 unwound from the coil 9 in thecontainer 77 is passed into the tube 1 through an optical fiber guide 81and the flared end 3 of the tube 1. Because only the leading end 8 ofthe optical fiber 7 is inserted in the tube 1, the conveying force thevibrating tube 1 exerts on the optical fiber 7 is limited to the lead-insection 2 of the tube. Accordingly, the conveying fource is too small tounwind the fiber 7 from the coil 9 and carry it to the flared end 3 thatportion of the optical fiber 7 which follows the lead-in section 2. Thelength of the preliminarily inserted optical fiber is between a fewmeters and ten-plus meters, varying with the size and surface conditionof the tube 1 and optical fiber 7 and the condition of the coil 9 of theoptical fiber 7. A pull force on the order of several tens of gramsworks on the optical fiber 7 as a result of the preliminary insertion.The preliminary insertion is done either manually or by feeding throughpinch rolls.

When preparations for passing are complete, drive motors 21, 22 arestarted. Carried forward by the action of helical vibrations, theoptical fiber 7 unwound from the coil 9 in the optical fiber container77 continuously moves into the tube 1 through the flared end 3 thereof.

PREFERRED EMBODIMENT V

FIGS. 11 and 12 show yet another embodiment of this invention.

A guide tube 107 is fastened to the cover 79 of an optical fibercontainer 77. The guide tube 107 extends from the top of the container77 to a roll feeder 57.

A roll feeder 110 is disposed on the exit side of the guide tube 107. Asshown in FIG. 13, the roll feeder 110 has a drive roll 112 rotatably setin a housing 111. The drive roll 112 is rotated by a gear motor 114whose speed, in turn, is controlled by a speed controller 115. To thehousing 111 is connected an arm 117 by means of a pin 118. The arm 117carries a rotatably mounted hold-down roll 120 at the tip thereof. Thearm 117 is manually rotated about the pin 118 to bring the hold-downroll 120 into and out of contact with the drive roll 112. The drive roll112 and hold-down roll 120 are respectively covered with rubber tires113, 121. The drive roll 112 and hold-down roll 120 hold the opticalfiber 7 from the guide tube 107 under the weight of the hold-down roll120. The rotation of the drive roll 112 sends the optical fiber 7 intothe inlet end 4 of the tube.

A tube holder 124 is disposed on the exit side of the roll feeder 110,with an optical fiber feed condition sensor 47 placed therebetween. Asshown in FIG. 13, the tube holder 124 comprises an outer cylinder 124,an intermediate cylinder 125 and an inner cylinder 127. A stand 129fastens the outer cylinder 125 to the floor 10. A number of rotatableballs 130 are fitted on the intermediate cylinder 126. The balls 130projecting on both sides of the intermediate cylinder 126 are in contactwith the inner surface of the outer cylinder 125 and the outer surfaceof the inner cylinder 127. Therefore, the inner cylinder 127 is allowedto rotate and move axially, but not permitted to move diametrically. Atop ring 131 is fitted near each end of the inner cylinder 127 toprevent the disengagement thereof from the outer cylinder 125.

The inlet end 4 of the tube is inserted in the inner cylinder 127 of thetube holder 124 and fastened with a setscrew 132. The roll feeder 110pulls out the looped up optical fiber 7 from the top end thereof. Theoptical fiber 7 is then fed to the tube 1 through the guide tube 107,roll feeder 110, optical fiber feed condition sensor 47 and tube holder124.

Referring to FIG. 14, the advance of the optical fiber 1 into the tube 1immediately after the start of insertion will be described now. Near theflared end 3, the tube 1 is allowed to move only axially, notdiametrically. Therefore, the inner wall of the vibrating tube exercisesno conveying force on the optical fiber 7 in this region. But the rollfeeder 110 advances the leading end 8 of the optical fiber 7. Thevibration of the tube also reduces the friction between the leading end8 of the optical fiber 7 and the inner wall of the tube, therebyfacilitating the action of the roll feeder 110 to advance the leadingend 8 of the optical fiber 7.

In a positive vibration area following the area in which diametricalvibration is inhibited, the diametrical component of vibration increasesprogressively. No force to check advance (owing to the centrifugaleffect and the static inertia of the optical fiber behind) works on theleading end of the optical fiber 7 in this region because the opticalfiber 7 in the upstream diametric vibration inhibited area is inside thetube and, in addition, under the influence of the driving force exertedby the roll feeder 110. Accordingly, the conveying force owing tovibration causes the optical fiber 7 to advance when the leading endthereof enters the positive vibration area. When the leading end of theoptical fiber 7 reaches the remotest end 5 of the lead-in section 2 ofthe tube, the remotest end 5 is at the uppermost end of the coil 6 ofthe tube. Thus, the optical fiber 7 is passed into the tube 1substantially tangentially to the coil 6. When the optical fiber 6 hasthus been properly brought into the regular passing position, the driveroll 112 of the roll feeder 110 is stopped, with the hold-down roll 67being retracted above away from the optical fiber. After this, the driveroll 112 serves as a guide to hold the optical fiber.

In the above example, the drive roll 112 of the roll feeder 110 can bestopped and functionally switched into a holding guide after the opticalfiber 7 has been brought into the passing position. But the drive roll112 may instead be allowed to continue driving even in that state. Inthis instance, the feed rate of the optical fiber is adjusted so thatthe speed with which the optical fiber 7 is fed to the flared end 3 ofthe tube is below the speed of the optical fiber 7 conveyed by theaction of vibration. That is, the roll feeder 110 exerts a braking forceon the optical fiber 7 being passed into the tube 1. This permitsadjusting the surplus length of the optical fiber 7 in the tube 1. Thesurplus length increases as the feed rate of the optical fiber becomescloser to the speed of the optical fiber 7 conveyed forward by helicalvibration, and vice versa. By the same method, the undulation of theoptical fiber passed through the tube can be reduced, too. The less theundulation, the fewer will be the chances of the optical fiber coming incontact with the top surface of the inner wall of the tube. Then, theoptical fiber is passed forward more smoothly.

The optical fiber 7 passed into the tube 1 must have a proper surpluslength. FIG. 15(a) shows an optical fiber 7 with an insufficient surpluslength. Such an optical fiber involves the risk of breaking, unable tofollow an elongation that might occur when temperature changes. FIG.15(b) shows an optical fiber with a proper surplus length. FIG. 15(c)shows an optical fiber with an excess surplus length. Such an opticalfiber bends more, receives greater pressure from the tube wall and,thus, travels forward less smoothly. An appropriate surplus length canbe obtained by adjusting the feed rate of the optical fiber as describedabove.

An optical fiber 7 being passed into a tube 1 may sag between the rollfeeder 110 and tube holder 124. On detecting a sag, the optical fiberfeed condition sensor 47 sends a signal to decelerate the drive roll 112of the roll feeder 110, thereby eliminating the sag. The drive roll 112stops when the sagging of the optical fiber 7 exceeds a preset limit.

PREFERRED EMBODIMENT VI

FIG. 16 shows still another embodiment of this invention.

This embodiment is a modified version of the preferred embodiment IIshown in FIG. 6. This embodiment differs from the embodiment II in FIG.6 in that the inlet end of the tube is longitudinally movable and thatthe optical fiber 7 from a feed spool 34 is directly fed to a guide tube135. Part of the feed spool 34 on an optical fiber feeder 33 projectsforward from the floor 10, with the straight guide tube 135 verticallydisposed directly thereunder. In this embodiment, the rotating speed ofthe feed spool 34 is adjusted so that the feed rate of the optical fiber7 to the inlet end 3 of the tube is below the speed with which theoptical fiber is conveyed forward by the action of vibration. An opticalfiber feed condition sensor of the type described before may beinstalled to detect the sagging of the optical fiber 7. Then, therotation of the feed spool 34 may be either decelerated or stoppedaccording to the amount of sagging detected.

PREFERRED EMBODIMENT VII

FIG. 17 shows a seventh embodiment of this invention.

An optical fiber feeder 33 and an optical fiber feed condition sensor 47are disposed diagonally above a bobbin 27. A bent optical fiber guide138 is provided on the exit side of the optical fiber feed conditionsensor 47. The guide 138 leads the optical fiber 7 from the opticalfiber feed condition sensor 47 to an optical fiber guide 140. The inletand outlet ends of the guide 138 should preferably have a smoothlymachined curved surface. To ensure that the falling of the optical fiber7 under gravity is not inhibited, the guide 138 must be made of materialwith a low coefficient of friction such as glass and plastics.

An optical fiber intake guide 140 is disposed directly below the guide138. The main portion 141 of the intake guide 140 is shaped like atrumpet as shown in FIG. 18, having a slit 142 that opens upward. Theintake guide 140 is suspended from the top flange 29 of the bobbin 27 bymeans of a metal holder 144.

Provision may be made in the guide 138 or optical fiber intake guide 140to apply a solid lubricant, such as a powder of carbon, talc, andmolybdenum disulfide on the surface of the optical fiber 7 passingtherethrough.

In this apparatus, the inlet end 4 of the tube is fastened to the topflange 29 of the bobbin 27 with a metal fastener 146. Then, thesmaller-diameter end of the intake guide proper 141 is connected to thetip 3 of the tube. Referring now to FIGS. 18 and 19, the forward motionof the optical fiber 7 at the inlet of the tube 1 will be described. Theoptical fiber 7 fed from the optical fiber feeder 33 to the bend 138falls through the slit 142 into the optical fiber intake guide 140 underits own weight. The optical fiber intake guide 140 vibrates togetherwith the coil 6 of the tube. Therefore, the optical fiber 7 in theintake guide 140 enters the tube from the lead-in section 2 thereof,under the influence of the conveying force produced by the vibration Vof the inner wall of the guide. The slit 142 in the intake guide 140 isof such width that the edges 143 thereof remain out of contact with theoptical fiber 7 fed from above even when the guide 140 vibrates togetherwith the bobbin 27. Therefore, the optical fiber 7 does not spring outfrom the inlet end 3 of the vibrating tube.

PREFERRED EMBODIMENT VIII

FIG. 20 shows an eighth embodiment of this invention, which is amodified version of the fourth embodiment. A major difference from thefourth embodiment is that the inlet end of the tube is not fastened.

A deflector roll 149 is provided directly above an optical fibercontainer 77 beside a bobbin. A guide roll 150 is disposed near theinlet end of the tube. The conveying force resulting from vibrationpulls out the optical fiber 7 along the axis of a coil 9 thereof in thecontainer 77. Supported and led by the deflector roll 149 and guide roll150, the optical fiber 7 thus pulled out travels to the inlet end 3 ofthe tube.

With the apparatus just described, the passing operation can be carriedout in the same way as with the foregoing embodiments, except thatpreliminary insertion is indispensable. The deflector roll 149 and guideroll 150, whose function is only to support and guide the optical fiber7, may be either rotatable or stationary.

PREFERRED EMBODIMENT IX

FIG. 21 shows a ninth embodiment of this invention, which is a modifiedversion of the fifth embodiment. A major difference from the fifthembodiment is that the inlet end of the tube is not fastened.

A roll feeder 110 is disposed next to a guide tube 107 fastened to thecover 79 of an optical fiber container 77 on the exit side thereof. Theexit end of the roll feeder 110 is close to the inlet end of the tube.Though not shown, the roll feeder 110 has a gear motor 114 and a speedcontroller 115 of the type shown in FIG. 13.

With the apparatus just described, the passing operation can be carriedout in the same way as with the foregoing embodiments. No preliminaryinsertion is needed. This apparatus permits pushing the optical fiber 7into the tube 1 as required. Or otherwise, a brake may be applied to theoptical fiber 7 carried forward by the force of vibration. In the lattercase, the braked optical fiber 7 in the tube 1 is pulled backward. Theresulting reduction in undulation permits a stable insertion of theoptical fiber 7 as described previously.

Preferred embodiments VIII and IX can be designed as simple structures.

PREFERRED EMBODIMENT X

FIG. 22 shows a last embodiment of this invention, which is a modifiedversion of the fifth embodiment. A major difference from the fifthembodiment is that a second roll feeder is provided on the exit side ofan optical fiber container to pull out an optical fiber therefrom.

As shown in the drawing, a second roll feeder 153, a second opticalfiber feed condition sensor 155 and a support guide 157 are disposedbetween an optical fiber container 77 and a first roll feeder 110. Thesecond roll feeder 153 and second optical fiber feed condition sensor155 are of the same structure as the first roll feeder 110 and the firstoptical fiber feed condition sensor 47. The support guide 157 is of thesame design as the support guide 54 shown in FIG. 1. The length of thesupport guide 157 is determined according to the distance between abobbin 27 and an optical fiber container 77. For example, when theoptical fiber container 77 is separated from the bobbin 27 (by, forinstance, 10 m), the length of the support guide 157 is increasedaccordingly.

The second roll feeder 153 feeds the optical fiber 7 pulled out of theoptical fiber container 77 to the first roll feeder 110. The opticalfiber 7 is fed to the first roll feeder 110 in such a manner as to sagbetween the second roll feeder 153 and support guide 157. Consequently,no tension works on the optical fiber 7 while being fed to the firstroll feeder 110. The second roll feeder 153 ensures the pull-out of theoptical fiber 7 from the optical fiber container 77. In this embodiment,a tube holder 124 holds the inlet end of the tube. But the inlet endneed not be held when the tube length is relatively short.

EXAMPLE

In order to confirm the effect of this invention, an optical fiber waspassed through a steel tube, using the apparatus shown in FIG. 11, underthe following conditions:

(1) Test Specimens

Coils of steel tubes:

Seven different coils (having 10 to 20 layers of rings), each beingwound around a steel bobbin having a barrel diameter of 1200 mm in goodorder, of seven different steel tubes 10 km in length, having an outsidediameter of 0.8 mm to 2.0 mm and an inside diameter of 0.5 mm to 1.6 mm.

Optical fibers:

Quartz glass optical fiber (125 μm in diameter) coated with siliconeresin, having a diameter of 0.4 mm.

(2) Vibrating Condition

Having 10 to 20 layers of rings, each coil of the steel tube testedvibrated substantially equally at all points thereof.

Angle of vibration with respect to the horizontal plane of the coil: 15degrees

Frequency of vibration: 20 Hz

Vertical component of total amplitude: 1.25 mm-1.55 mm

(3) Roll Feeder

When the optical fiber has been put in the steady passing condition, thedrive roll of the roll feeder is stopped to function as an optical fibersupport guide, with the hold-down roll retracted.

Under the above conditions, the optical fibers were smoothly passedthrough the steel tubes without any hitch. It was confirmed that theoptical fibers were passed through the entire length of the steel tubeswithin a given length of time at a speed of 2 m/min. to 4 m/min. Nodifficulty was encountered even in passing an optical fiber through atube whose diameter was as small as 2 mm or under and whose length wasas large as about 10 km. Of course, the optical fibers passed throughthe steel tubes suffered no degeneration.

To adjust the amount of surplus length and the magnitude of undulation,the feed roll feeder was always kept in motion. The speed of the driveroll was adjusted to control the feed rate of the optical fiber withinthe range of 40% to 95% of the conveyance speed owing to vibration. Allthis resulted in the attainment of appropriate surplus length and thesuppression of undulation, thereby assuring a smooth travel of theoptical fiber through the steel tube.

Though the threadlike piece was optical fibers in the preferredembodiments described herein, this invention is also applicable to thepassing of other types of threadlike pieces, such as wires of suchmetals as copper and steel and of such nonmetallic substances asplastics. The number of threadlike pieces passed through a tube is notlimited to one. Multiple threadlike pieces may be passed through a tubeif the inside diameter of the tube and the diameter of the threadlikepieces permit. The tube need not be of steel, but may be of many othertypes of materials, such as aluminum and synthetic resins. Any othersubsequent process, such as surface polishing, may be added to thepassing of the threadlike piece through the metal tube as desired.Although not always necessary, the central axis of the coil of the tubeshould preferably coincide with the central axis of a helix and extendvertically. Furthermore, other combinations of the spools, feeders,inlet end holders and other means than those disclosed hereabove arealso included within the scope of this invention.

What is claimed is:
 1. A method of passing a threadlike piece through atubular product which comprises the steps of:forming a coil of a tubehaving an inlet end; and vibrating the coil of the tube while feeding athreadlike piece through the inlet end of the tube so that a given pointof the tube reciprocates along a helical path, said feeding of thethreadlike piece being made in such a manner that the inlet end of thetube does not diametrically move a portion of the threadlike pieceupstream of and close to the inlet end of the tube.
 2. A method ofpassing a threadlike piece through a tubular product according to claim1, in which said motion of the threadlike piece is prevented byfastening a point of the tube near the inlet end thereof to keep theinlet end of the tube at a standstill.
 3. A method of passing athreadlike piece through a tubular product according to claim 1, inwhich said motion of the threadlike piece is prevented by fastening apoint of the tube near the inlet end thereof so that the inlet end ofthe tube is allowed to move longitudinally, but not diametrically.
 4. Amethod of passing a threadlike piece through a tubular product accordingto claim 1, in which said motion of the threadlike piece is prevented byfeeding the threadlike piece to the inlet end of the tube through anupward opening of a guide that extends substantially horizontally, andis connected to the inlet end of the tube so as to vibrate together withthe coil of the tube.
 5. A method of passing a threadlike piece througha tubular product according to any of claims 1 to 3, in which thethreadlike piece is fed to the inlet end of the tube whose lead-insection is separated from a coil thereof and curved upright.
 6. A methodof passing a threadlike piece through a tubular product according to anyone of claims 1 to 4, in which a coil of the threadlike piece is formedand the threadlike piece is pulled out therefrom along an axis and fedto the tube by a conveying force produced by vibration acting on thethreadlike piece in the tube.
 7. A method of passing a threadlike piecethrough a tubular product according to any one of claims 1 to 3, inwhich the threadlike piece is sent to the inlet end of the tube by meansof a feeder disposed near the inlet end of the tube at least during theinitial stage of passing.
 8. A method of passing a threadlike piecethrough a tubular product according to any one of claims 1 to 3, inwhich the threadlike piece is positively sent forward in such as mannera to follow a rate of conveyance of the threadlight piece produced byvibration.
 9. A method of passing a threadlike piece through a tubularproduct according to anyone of claims 1 to 3, further comprisingcontrolling a feed rate of the threadlike piece upstream of the inletend of the tube so that the speed of the threadlike piece is determinedby the feed rate thereof.
 10. A method of passing a threadlike piecethrough a tubular product according to claim 9, in which the threadlikepiece is passed into the tube at the running speed of a feeder disposednear the inlet end of the tube for pushing the threadlike piece therein.11. A method of passing a threadlike piece through a tubular productaccording to claim 9, further comprising controlling a feed rate of thethreadlike piece so that the feed rate thereof to the inlet end of thetube is kept below a speed of conveyance of the threadlike pieceproduced by vibration.
 12. A method of passing a threadlike piecethrough a tubular product which comprises the steps of:forming a coil ofa tube having an inlet end; forming a coil of a threadlike piece; andvibrating the coil of tube so that a given point of the tubereciprocates along a helical path, and the threadlike piece is pulledout from the coil along an axis and fed into the tube.
 13. A method ofpassing a threadlike piece through a tubular product according to claim12, in which the threadlike piece is pulled out from a coil thereofalong an axis and fed into the tube by conveying force produced byvibration acting on the threadlike piece in the tube.
 14. A method ofpassing a threadlike piece through a tubular product according to claim12, in which the threadlike piece is pulled out from a coil thereofalong the axis thereof and fed into the tube by means of a feeder.
 15. Amethod of passing a threadlike piece through a tubular product accordingto any one of claims 12 to 14, in which a reversed twist is given to thethreadlike piece being formed into a coil in order to offset a twistthat occurs about the axis of the threadlike piece when the threadlikepiece is pulled out of the coil thereof.
 16. A method of passing athreadlike piece through a tubular product according to any one ofclaims 12 to 14, in which the threadlike piece is fed to the inlet endof the tube whose lead-in section is separated from a coil thereof andcurved upright.
 17. A method of passing a threadlike piece through atubular product according to any one of claims 12 to 14, in which a longenough portion of the threadlike piece to produce a large enoughconveying force to pull the threadlike piece into the tube ispreliminarily inserted into the tube through the inlet end thereof. 18.A method of passing a threadlike piece through a tubular productaccording to any one of claims 12 to 14, in which the feed rate of thethreadlike piece is controlled so that the speed with which thethreadlike piece is fed to the inlet end of the tube is kept below aspeed of conveyance of the threadlike pieces produced by vibration. 19.A method of passing a threadlike piece through a tubular productaccording to claim 14, in which the threadlike piece is positively sentforward in such a manner as to follow a speed of conveyance of thethreadlike piece produced by vibration.
 20. An apparatus for passing athreadlike piece through a tubular product which comprises:means forsupporting a coil of a tube having an inlet end and an inner wall andinto which a threadlike piece is to be passed; means for holding a pointof the tube near the inlet end thereof so that a portion of thethreadlike piece upstream of and close to the inlet end of the tube isnot diametrically moved by the inlet end of the tube; means forvibrating said tube coil supporting means in such a manner that a givenpoint of the tube reciprocates along a helical axis; and means forfeeding the threadlike piece through the inlet end of the tube whosecoil is being vibrated, an intermittent conveying force the inner wallof the tube exerts in the direction of the circumference of the coil onthe threadlike piece in the tube causing the threadlike piece to advancethrough the tube while keeping the threadlike piece from springing outfrom said inlet end.
 21. An apparatus for passing a threadlike piecethrough a tubular product according to claim 20, in which the tube coilsupporting means comprises a cylindrical member.
 22. An apparatus forpassing a threadlike piece through a tubular product according to claim20, in which the means for holding the point of the tube near the inletend thereof comprises means that fastens 9 lead-in section of the tubein such a manner that the inlet end of the tube is at a standstill. 23.An apparatus for passing a threadlike piece through a tubular productaccording to claim 20, in which the means for holding the point of thetube near the inlet end thereof comprises means that fastens the pointof the tube near the inlet end thereof in such a manner that the inletend of the tube is allowed to move longitudinally while being prohibitedfrom moving diametrically.
 24. An apparatus for passing a threadlikepiece through a tubular product according to claim 20, in which themeans for holding the point of the tube near the inlet end thereofcomprises a stand, a casing supported by the stand and pairs of guiderolls rotatably supported by the casing, the pairs of guide rolls tohold therebetween the point of the tube near the inlet end thereof beingalternately disposed in a vertical and a horizontal position.
 25. Anapparatus for passing a threadlike piece through a tubular productaccording to claim 20, in which the means for holding the point of thetube near the inlet end thereof comprises a stand, an outer cylindersupported by the stand, an intermediate cylinder passed through theouter cylinder, an inner cylinder passed through the intermediatecylinder, the inner cylinder being adapted to receive and fasten thepoint of the tube near the inlet end thereof passed therein, and a largenumber of balls rotatably attached to the intermediate cylinder.
 26. Anapparatus for passing a threadlike piece through a tubular productaccording to claim 20, in which the means for feeding the threadlikepiece comprises a rotatably supported spool carrying the threadlikepiece wound therearound.
 27. An apparatus for passing a threadlike piecethrough a tubular product according to claim 26, in which means fordriving the spool is provided.
 28. An apparatus according to claim 27 inwhich:said means for supporting a coil of the tube comprises a base, avibrating table mounted on the base with a spring disposed therebetween,and a bobbin to carry a coil of the tube wound therearound fastened onthe vibrating table so that the axis of the bobbin coincides with thecentral axis of said helix; said vibrating means comprises a vibratingmotor having weights disposed eccentric to the axis of rotation andattached to the vibrating table, the vibrating motor vibrating thevibrating table so that a given point thereof reciprocates along a helixhaving a vertical central axis; a sensor to detect a difference betweenthe passing speed and the feed rate of the threadlike piece; and meansfor controlling said spool driving means on the basis of the speeddifference detected by the sensor.
 29. An apparatus for passing athreadlike piece through a tubular product according to claim 20, inwhich the means for feeding the threadlike piece comprises a stationarybobbin carrying the threadlike piece wound therearound.
 30. An apparatusfor passing a threadlike piece through a tubular product according toclaim 20, in which the means for feeding the threadlike piece comprisesa container to hold a coil of the threadlike piece that opens upward.31. An apparatus according to claim 30 in which:said means forsupporting a coil of the tube comprises a base, a vibrating tablemounted on the base with a spring disposed therebetween, and a bobbin tocarry a coil of the tube wound therearound fastened on the vibratingtable so that the axis of the bobbin coincides with the central axis ofsaid helix; said threadlike piece feeding means comprises a roll feederhaving a driven roll and disposed between the bobbin and the threadlikepiece container; said vibrating means comprises a vibrating motor havingweights disposed eccentric to the axis of rotation and attached to thevibrating table, the vibrating motor vibrating the vibrating table sothat a given point thereof reciprocates along a helix having a verticalcentral axis; said threadlike piece feed rate controlling meanscomprises means for controlling a rotating speed of a driven roll of aroll feeder; and sensor to detect a difference between a speed and thefeed rate of the threadlike piece, the rotating speed of the driven rollof the roll feeder being controlled on the basis of the speed differencedetected by the sensor.
 32. An apparatus for passing a threadlike piecethrough a tubular product according to claim 20, in which the means forfeeding the threadlike piece is disposed above a coil of the tube andhas means for guiding the threadlike piece, the guiding means comprisinga vertical guide interposed between the threadlike piece feeding meansand the inlet end of the tube.
 33. An apparatus for passing a threadlikepiece through a tubular product according to claim 20, in which a feederfor exerting a longitudinal force on the threadlike piece is disposedbetween the threadlike piece feeding means and means for holding thepoint of the tube near the inlet end thereof.
 34. An apparatus forpassing a threadlike piece through a tubular product according to claim33, in which the feeder is adapted to positively send the threadlikepiece to the inlet end of the tube.
 35. An apparatus for passing athreadlike piece through a tubular product according to claim 33, inwhich the feeder exerts a braking force on the threadlike piece enteringthe inlet end of the tube.
 36. An apparatus for passing a threadlikepiece through a tubular product according to claim 33, in which a feederto pull out the threadlike piece from the threadlike piece feedingmeans, threadlike piece feed condition sensing means disposed betweenthe feeder and threadlike piece pull-out feeder and means to control thespeed of the pull-out speed of the feeder on the basis of a signal fromthe threadlike piece feed condition sensing means are provided betweensaid threadlike piece feeding means and feeder.
 37. An apparatus forpassing a threadlike piece through a tubular product whichcomprises:means for supporting a coil of a tube having an inlet end andan inner wall and into which a threadlike piece is to be passed; meansfor holding a coil of the threadlike piece in such a manner as to permitthe threadlike pieces to be pulled out along the axis of the coil; andmeans for vibrating said tube coil supporting means in such a mannerthat a given point of the tube reciprocates along a helical axis, thethreadlike piece being fed through the inlet end of the tube whose coilis being vibrated, and an intermittent conveying force the inner wall ofthe tube exerts circumferentially of the coil on the threadlike piece inthe tube causing the threadlike piece to advance through the tube. 38.An apparatus for passing a threadlike piece through a tubular productaccording to claim 37, in which the tube coil supporting means comprisesa cylindrical member.
 39. An apparatus for passing a threadlike piecethrough a tubular product according to claim 37, in which the means forholding the coil of the threadlike piece comprises a stationary bobbincarrying the threadlike piece wound therearound.
 40. An apparatus forpassing a threadlike piece through a tubular product according to claim37, in which the means for holding the coil of the threadlike piececomprises a container to hold a coil of the threadlike piece that opensupward.
 41. An apparatus according to claim 40 in which:said means forsupporting a coil of the tube comprises a base, a vibrating tablemounted on the base with a spring disposed therebetween, and a bobbin tocarry a coil of the tube wound therearound fastened on the vibratingtable so that the axis of the bobbin coincides with a central axis ofsaid helix; said vibrating means comprises a vibrating motor havingweights disposed eccentric to the axis of rotation and attached to thevibrating table, the vibrating motor vibrating the vibrating table sothat a given point thereof reciprocates along a helix having a verticalcentral axis; and a guide roll disposed above the container to guide thethreadlike piece pulled out of the container to the inlet end of thetube.
 42. An apparatus according to claim 40 in which:said means forsupporting a coil of the tube comprises a base, a vibrating tablemounted on the base with a spring disposed therebetween, and a bobbin tocarry a coil of the tube wound therearound fastened on the vibratingtable so that the axis of the bobbin coincides with a central axis ofsaid helix; said vibrating means comprises a vibrating motor havingweights disposed eccentric to the axis of rotation and attached to thevibrating table, the vibrating motor vibrating the vibrating table sothat a given point thereof reciprocates along a helix having a verticalcentral axis; and a roll feeder disposed between the bobbin and thethreadlike piece container to lead the threadlike piece pulled out ofthe container to the inlet end of the tube.
 43. An apparatus for passinga threadlike piece through a tubular product according to claim 37, inwhich the means for holding the coil of the threadlike piece is disposedabove a coil of the tube and has means for guiding the threadlike piece,the guiding means comprising a vertical guide and being interposedbetween the threadlike piece feeding means and the inlet end of thetube.
 44. An apparatus for passing a threadlike piece through a tubularproduct which comprises:means for supporting a coil of a tube having aninlet end and an inner wall and into which a threadlike piece is to bepassed; means for feeding the threadlike piece to the inlet end of thetube; means for vibrating said tube coil supporting means in such amanner that a given point of the tube reciprocates along a helical path,an intermittent conveying force the inner wall of the tube exertscircumferentially of the coil on the threadlike piece in the tubecausing threadlike piece to advance through the tube; and means forcontrolling the feed rate of the threadlike piece by adjusting the forceworking on the threadlike piece in the longitudinal direction thereofupstream of the inlet end of the tube so that the speed of thethreadlike piece is determined by the feed rate thereof.
 45. Anapparatus for passing a threadlike piece through a tubular productaccording to claim 44, in which the tube coil supporting means comprisesa cylindrical member.
 46. An apparatus for passing a threadlike piecethrough a tubular product according to claim 44, in which the means forfeeding the threadlike piece comprises a rotatably supported spoolcarrying the threadlike piece wound therearound.
 47. An apparatus forpassing a threadlike piece through a tubular product according to claim46, in which means for driving the spool is provided.
 48. An apparatusas claimed in claim 46 in which:said means for supporting a coil of thetube comprises a base, a vibrating table mounted on the base with aspring disposed therebetween, a vibrating motor having weights disposedeccentric to the axis of rotation and attached to the vibrating table,the vibrating motor vibrating the vibrating table so that a given pointthereof reciprocates along a helix having a vertical central axis, and abobbin to carry a coil of the tube wound therearound fastened on thevibrating table so that the axis of the bobbin coincides with a centralaxis of said helix; said spool being disposed above the bobbin forfeeding the threadlike piece into the tube wound around the bobbinthrough the inlet end thereof; a sensor to detect a difference betweenthe passing speed and the feed rate of the threadlike piece; means forcontrolling said spool driving means on the basis of the speeddifference detected by the sensor; a guide tube extending downward froman exit side of the sensor; and an intake guide comprising a guideproper extending substantially horizontally and fastened to the bobbin,the guide proper having a smaller-diameter end connected to the inletend of the tube and a slit opening upward through which the threadlikepiece falling down from the guide tube being led into the guide proper,the intake guide being adapted to vibrate together with the bobbin toexert on the threadlike piece held therein a conveying force working inthe direction of the inlet end of the tube.
 49. An apparatus for passinga threadlike piece through a tubular product according to claim 44, inwhich the means for feeding the threadlike piece comprises a stationarybobbin carrying the threadlike piece wound therearound.
 50. An apparatusfor passing a threadlike piece through a tubular product according toclaim 44, in which the means for feeding the threadlike piece comprisesa container to hold a coil of the threadlike piece that opens upward.51. An apparatus for passing a threadlike piece through a tubularproduct according to claim 44, in which the means for feeding thethreadlike piece is disposed above a coil of the tube and has means forguiding the threadlike piece, the guiding means comprising a verticalguide interposed between the threadlike piece feeding means and theinlet end of the tube.
 52. An apparatus for passing a threadlike piecethrough a tubular product according to claim 44, in which the feed ratecontrol means comprises means for positively feeding the threadlikepiece to the inlet end of the tube.
 53. An apparatus for passing athreadlike piece through a tubular product according to claim 44, inwhich the feed rate control means comprises means for exerting a brakingforce on the threadlike piece entering the inlet end of the tube.
 54. Anapparatus for passing a threadlike piece through a tubular productaccording to claim 44, in which the feed rate control means comprises anelectromagnetic feeder.
 55. An apparatus for passing a threadlike piecethrough a tubular product according to claim 44, in which the feed ratecontrol means comprises a belt feeder.
 56. An apparatus for passing athreadlike piece through a tubular product according to claim 44, inwhich the feed rate control means comprises a roll feeder.
 57. Anapparatus for passing a threadlike piece through a tubular productaccording to claim 44, in which means for sensing a difference between aspeed and feed rate of the threadlike piece disposed between the feedrate control means and the inlet end of the tube and means forcontrolling the feed rate control means on the basis of a signal fromsaid speed difference sensing means are provided.
 58. An apparatus forpassing a threadlike piece through a tubular product according to claim57 in which the speed difference sensing means comprises an image sensorto detect the vertical motion or sagging of the threadlike piece.
 59. Amethod of passing a threadlike piece through a tubular product accordingto claim 5 in which the threadlike piece is sent to the inlet end of thetube by means of a feeder disposed near the inlet end of the tube atleast during the initial stage of passing.
 60. A method of passing athreadlike piece through a tubular product according to claim 5 in whichthe threadlike piece is positively sent forward in such a manner as tofollow a rate of conveyance of the threadlike piece produced byvibration.
 61. A method of passing a threadlike piece through a tubularproduct according to claim 5 further comprising controlling a feed rateof the threadlike piece upstream of the inlet end of the tube so thatthe speed of the threadlike piece is determined by the feed ratethereof.